1. Field of the Invention
The present invention relates to an elastic crawler for endless crawler vehicles for use in the fields of construction, engineering, agriculture and the like.
2. Description of the Related Art
An elastic crawler (rubber crawler), in which a plurality of core metals having right and left wings, respectively, are provided laterally and in parallel with a space in the longitudinal direction of the crawler between the core metals in a crawler body formed of an elastic material into a band shape with no end, and right and left lugs are provided so as to be raised on positions overlapping projected planes of the above right and left wings on a ground-contacting surface side of the above crawler body and allotted to right and left of the center in the widthwise direction of the crawler body, is known in the Japanese Examined Patent Publication No. Hei-79549 and publications of Japanese patents No. 2654926 and No. 2609801, for example.
The above conventional elastic crawler has a basic structure in which lugs having a ground-contacting surface having a length in a circumferential direction covering (extending to) projected planes of two core metal wings adjacent in the longitudinal direction of the crawler on a ground-contacting surface side of the crawler body, are allotted to right and left of the center in the widthwise direction of the crawler body.
In the elastic crawler (rubber crawler) disclosed in the aforementioned publications, the lugs are formed as raised portions allotted to right and left extend to the wings of the core metals adjacent in the longitudinal direction of the crawler so that the rigidity of the crawler body is redoubled, so as to improve endurance of the lugs, thereby improving endurance of the crawler itself.
In the above elastic crawler, however, since all the lugs allotted to right and left are configured to extend to (cover) the two core metal wings adjacent in the longitudinal direction of the crawler, flexing properties at a wrapping section (a section for wrapping the crawler around a driving wheel, for example) are deteriorated due to the lugs. This results in an insufficient engagement with a driving claw, causing a risk of come-off of the crawler from wheels.
Furthermore, in the crawler body, since the rigidity at portions on which lug are formed is large while the rigidity at portions without lugs between the lugs in a longitudinal direction of the band of the crawler body is small. Since the rigidity at the portions with lugs and that at the portions without lugs are remarkably different, and the large and small rigidity portions are arranged in turn across a whole length of the crawler, a crack at a root of the lugs may be caused by a large distortion centered. When the crack becomes large, water or the like penetrated through the crack rusts the core metal or a steel code as a tension resistance body, deteriorating the endurance of the crawler.
The above problem can be solved to a certain degree by forming a concave groove corresponding to a portion between the core metal wings of the lugs (refer to Japanese Patent No. 2654926).
Forming a concave groove on a ground-contacting surface of the lugs, however, causes vibration. The vibration transmitted to and felt by an operator (a driver) may not only cause fatigue, but also have a bad influence on every kind of mounted equipments, components and the like.
An object of the invention is to improve flexing properties at a wrapping section by contriving an arrangement of lugs with respect to core member wings to avoid a cause of a crack at a root of a lug as well as reduce a cause of vibration, so that endurance of an elastic crawler is greatly improved as a whole.
In order to achieve the above-mentioned object, the following technical ways are taken in the present invention. An elastic crawler comprises a crawler body formed of an elastic material into an endless band shape, a plurality of core members having right and left wings, respectively, provided in the crawler body laterally relative to the crawler and in parallel to each other with a space therebetween in the longitudinal direction of the crawler, and right and left lugs provided so as to be raised at positions overlapping projected planes of the right and left wings on a ground-contacting surface of the crawler body on the right and left sides of the center in the widthwise direction of the crawler.
In an elastic crawler according to the invention, one of the right and left lugs has a ground-contacting surface extending to and overlapping projected planes of a plurality of wings on the same side as the lug adjacent each other in a longitudinal direction of the crawler and having a ground-contacting length in a circumference direction, while the other lug has a ground-contacting surface overlapping a projected plane of a wing on the same side as the lug and having another ground-contacting length in the circumference direction. The ground-contacting length of the latter lug is formed shorter than that of the former lug so that the right and left ground-contacting surfaces are different in the ground-contacting length, and the right and left lugs having the ground-contacting surfaces different in the ground-contacting length are arranged as a pair on the right and left sides of the center in the widthwise direction of the crawler to be staggered along the crawler.
Further, in an elastic crawler according to the invention, one of the above right and left lugs has a ground-contacting surface extending to and overlapping projected planes of two wings of the same side as the lug adjacent each other in the longitudinal direction of the crawler and having a ground-contacting length in a circumferential direction, while the other lug has a ground-contacting surface overlapping a projected plane of a wing on the same side as the lug and having another ground-contacting length in the circumference direction. The ground-contacting length of the latter lug is formed shorter than that of the former lug so that the right and left ground-contacting surfaces are different in the ground-contacting length, and the right and left lugs having the ground-contacting surfaces different in the ground-contacting length are arranged as a pair on the right and left sides of the center in the widthwise direction of the crawler to be staggered along the crawler.
As a result of adopting above structures in which the right and left lugs having the ground-contacting surfaces different in the ground-contacting length are staggered along the crawler and overlap the projected planes of the wings, the flexing properties at the wrapping section are improved and come-off of the crawler can be prevented.
Here, the projected planes of the right and left wings are overlapped entirely or a part of the width of the wings (length in the longitudinal direction of the crawler).
For circulating a crawler body in the longitudinal direction thereof, frictional drive by means of a driving drum provided at the wrapping section may be adopted. Alternately, a c law of a driving wheel for engaging the crawler body (driving sprocket) may be provided at the wrapping section.
In the case of adopting the latter means, it is recommended to form an engagement aperture f or engaging a driving wheel at the center in the widthwise direction of the crawler body and between the core members adjacent each other in the longitudinal direction of the crawler, and to protrusively form one of the lugs on one of right and left side peripheries of the engagement aperture and protrusively form the other lug on the other side periphery of the aperture at a position forward or rearward from the aperture in the longitudinal direction of the crawler.
It is also recommended that the ground-contacting length in the circumferential direction of the ground-contacting surface of one of the lugs extends to two adjacent core member wings disposed forwardly and rearwardly in the longitudinal direction of the crawler while the ground-contacting length in the circumferential direction of the ground-contacting surface of the other lug overlaps one core member wing, and the ground-contacting surface of the above other lug is shifted forwardly or rearwardly from a corresponding core member wing in order to form a continuous ground-contacting surface in the longitudinal direction of the crawler with the ground-contacting surfaces of the right and left lugs.
As a result of adopting such structure, vibration during driving can be restrained, thereby reducing vibration of a machine body, providing a driver with comfortable driving operation with no fatigue, and preventing troubles in equipment.
Furthermore, it is recommended that right and left protrusions for preventing come-off of the crawler are formed on the right and left sides in the center part in the widthwise direction of the crawler on a no-ground-contacting surface of each core member, the right and left protrusions being arranged to be offset from each other in the longitudinal direction of the crawler so as to be staggered along the crawler, and right and left grooves for flexion laterally extending in the widthwise direction of the crawler between core member wings adjacent each other in the longitudinal direction of the crawler, are formed on the no-ground-contacting surface of the crawler body.
As a result of adopting such structure, the flexing properties at the wrapping section are further improved, so that come-off of the crawler from rolling wheels can be surely prevented also with the right and left protrusions.